Field of the Invention
The present invention relates to mine detection, and specifically, to mine detection through laser interferometry.
Brief Description of Related Art
Buried land mines present themselves as interference fringe patters when insonified and imaged by a laser interferometer system. The indistinct nature of the patterns has made them a challenge to indemnify consistently with automated detection algorithms so they typically have been identified by visual analysis of the digital imagery. To fully exploit laser interferometer imagery within an operational system requires a means of automatically detecting these patterns.
Automatic detection of the interference signatures produced by buried mines present multiple challenges. Ordinary approaches to automated target detection are confounded by the distributed nature of the target signature and variations related to target materials, structure, and burial depth. Furthermore, target signatures often have low signal to noise ratio (SNR), embedded in a grainy background caused by laser speckle, so anomaly detection algorithms that are based on SNR of a distinct target shape may not detect them.
Derivative analysis is often utilized in spectroscopic research as it can help identify minute fluctuations in the shape of hyperspectral signatures. For example, peaks in the 2nd derivative of a reflectance spectrum can be used to identify specific absorption regions caused by biological pigments, paints, materials properties or any other feature that affects reflectance. The idea for the derivative peak detection algorithm originated from spectroscopy, but takes the concept and applies it to vectors of pixel intensity instead of spectral reflectance. Variations in intensity along the pixel vector are translated into a derivative spectrum that shows the location of the most rapid changes, similar to how the derivative of a reflectance spectrum shows the locations where reflectance changes rapidly due to pigment or material absorption.
The existing art all suffers from the defect that buried mines produce a unique pattern of parallel lines that varies in shape and intensity, making it difficult to detect using spectral or shape-based detections.